numbness vs numb

numbness is a noun but numb is not a noun.

Word	Noun	Adjective	Verb	Adverb
numbness	Yes	No	No	No
numb	No	Yes	Yes	No

numbness (noun)	numb (noun)
the trait of lacking enthusiasm for or interest in things generally
partial or total lack of sensation in a part of the body; a symptom of nerve damage or dysfunction

numbness (adjective)	numb (adjective)
	so frightened as to be unable to move; stunned or paralyzed with terror; petrified
	lacking sensation
	(followed by `to') not showing human feeling or sensitivity; unresponsive

numbness (verb)	numb (verb)
	make numb or insensitive